1. Field of the Invention
The present invention relates to a wheelchair cushion with pneumatically connected chambers, the inflation of which is monitored, for cushioning the coccyx, ischial tuberosities, greater trochanters and thighs.
2. Brief Description of the Prior Art
Patients confined to wheelchairs face the prospect of development of decubitus ulcers or "bed sores" on their buttocks, the best treatment of which is prevention. These ulcers form at bony locations when prolonged sitting pressure reduces blood circulation below the level required to sustain tissue life. Skin breakdown can also occur when the patient is seated on a wheelchair cushion that does not provide adequate ventilation and causes the skin to be excessively moist and warm for protracted periods. A healthy subject seated in a chair will feel pain or discomfort from the pressure and heat build up and change positions but if the patient is paralyzed, elderly or otherwise disabled, disoriented or sick, he may not be aware of the problem or may not be able to move. One additional factor contributing to tissue destruction is shear forces encountered between the patient's buttocks, clothing and the wheelchair cushion in sitting down or changing position.
Various wheelchair cushions have been proposed to reduce the risk of skin breakdown by spreading the patient's weight over his buttocks. Such cushions include air or fluid filled cushions, foam composition cushions and gel filled cushions. Gel and foam cushions produce too much pressure against the skin as they are compressed against the bony regions and contribute to moisture and heat build up. Fluid filled cushions (e.g., water) provide a heat sink but are heavy and subject to leaking. Air filled cushions have been provided in passive form (inflation pressure does not change) and in dynamic form (selected cells are alternately inflated and deflated). Passive air cushions as a group do not permit air to communicate easily with the seated surface and afford little opportunity for heat and humidity to be transferred away. In addition, when the cushion is thick enough to keep the patient from bottoming out, it is often unsteady and difficult for a person with impaired body balance to use. Passive air cushions are also susceptible to leaking. If the patient is paralyzed or is not aware of the leak, he may continue to sit on the deflated cushion and sustain tissue damage. Air cushions of the dynamic form also suffer from moisture and heat transfer problems when the air cells are made of vinyl and other moisture vapor impervious materials and, more importantly, are expensive. The aging of the "Baby Boomers" beginning in the next decade with the prospect of increasing numbers of wheelchair bound patients and the current political and media attention being given to health care costs, make affordability a major issue.